The invention relates to an electric lamp provided with:
a translucent lamp vessel having an axis and an end portion, PA1 a light source in the lamp vessel, PA1 a lamp cap comprising a sheath portion and a base portion, to which an end portion of the lamp vessel is adhesively bonded by means of a thermoplastic synthetic resin which synthetic resin adheres both to the lamp vessel and to the lamp cap, the lamp cap having an electric contact to which a current supply conductor to the light source is connected.
The invention further relates to the manufacture of such a lamp. Such a lamp is known from British Patent Specification No. 1,380,720.
In the known lamp, the lamp cap is bonded to the lamp vessel by means of a synthetic resin, for example a thermoplastic synthetic resin of the kind of which in this known lamp the lamp cap consists, i.e. a polysulphone or a polyketone. A ring of this polymer is arranged to surround the end portion of the lamp vessel and is caused to melt. Subsequently, the lamp cap is provided and a butt joint is obtained between the lamp vessel and the lamp cap by cooling the assembly.
It has been found that with the use of a this synthetic resin lamps are obtained which do not satisfy the IEC standard. In particular the adhesion of the polymer to the lamp vessel is too poor for the requirements imposed on the torsional strength of the connection between the lamp vessel and the lamp cap.